A scanning electron microscope (SEM) has been generally used as a testing device of a testing apparatus for conducting tests on a variety of products (test subjects), for example, a variety of tests on a semiconductor water, liquid crystal substrate, etc. in production processes.
Tests and measurements by a SEM in the above testing apparatus had to be performed by taking a test subject, such as a semiconductor wafer and a liquid crystal substrate, in a highly vacuumed vacuum chamber. This is because it is necessary to test or measure in a vacuum at the time of testing and measuring by the SEM using an electron beam so as to prevent the electron beam from scattering by collisions with gas molecules.
Note that tests conducted by using the above testing apparatus are, for example when the test subject is a semiconductor wafer, conducted at a stage of forming a resist pattern on a semiconductor wafer for improving yields and to test or measure whether the resist pattern has a predetermined shape (a width size and a length) and to inspect an existence of any lacks in the resist pattern, etc. Note that the reason why the test is conducted on the semiconductor wafer at this stage is because it is before an etching process, so that it is possible to reproduce the semiconductor wafer by removing the resist when the resist pattern has any defects.
However, in the above testing apparatus, a vacuum chamber having a capacity in accordance with a size of a test subject was necessary.
Namely, in the above testing apparatus, a test subject is loaded on a load portion of a conveying means, a position of the test subject is finely adjusted by the conveying means while checking the position by using an optical testing device, etc. and a part desired to be tested and the SEM and other testing device are aligned. Thus, the vacuum chamber is required to have a size capable of taking the test subject together with the load portion of the conveying means in a vacuum. Specifically, a load portion having an area of about four times of a surface to be tested of the test subject was necessary.
Also, in the above testing apparatus, to shorten a TAT (turn around time) of a test process including a waiting time for the test, in addition to the vacuum chamber, a load lock chamber for holding the test subject in a low vacuum state before carrying it into a highly vacuum state was also required for not carrying the test subject directly into the highly vacuum state. By taking the test subject in the load lock chamber before carrying it to the vacuum chamber, an air evacuation time can be made short at the time the test subject is taken in the vacuum chamber.
In recent years, liquid crystal substrates and semiconductor wafers as test subjects of the above testing apparatus have become larger in size, and those having a side length of 700 mm or more in the former and those having a diameter of 300 mm or more in the latter have appeared. Accordingly, when testing a semiconductor wafer having a diameter of 300 mm, the load portion of the test subject of the conveying means is required to have a space of at least a diameter of 600 mm.
Therefore, in a testing apparatus for a large-scaled test subject, a vacuum chamber having a size as explained above as well as a load lock chamber was necessary, so that there was a disadvantage that the overall apparatus became large. Also, since the vacuum chamber and the load lock chamber having a large capacity as explained above had to be evacuated by a large-scale vacuum pump every time a test subject was exchanged, it took an enormous energy and time and there was a disadvantage that a test in a short time was impossible.
Particularly, in the case of a large-scale test subject, such as a liquid crystal substrate, etc. which has rapidly become large-scaled, a load portion having an area of about four times of a surface to be tested of the test subject is necessary, so there are many problems in terms of a cost and a size as explained above to prepare a vacuum chamber having a size in accordance with the large-scaled liquid crystal substrate. Consequently, there was no other way but to conduct a so-called destructive random test by preparing a sample by cutting off a part thereof for testing, so that the test can be conducted by using a small-sized vacuum chamber.
Furthermore, in the above conventional testing apparatus, there was a disadvantage of being unable to handle a peculiarly shaped test subject which cannot be handled by making the vacuum chamber large, for example, a rolled steel plate having a several hundreds of meters and other long subjects.